Method and apparatus for transmitting enhanced uplink data using a H-ARQ process

ABSTRACT

A wireless transmit/receive unit (WTRU) is configured to configure a set of hybrid automatic repeat request (H-ARQ) processes. The WTRU is configured to receive information which limits a particular MAC-d flow to accessing a limited set of H-ARQ processes. The WTRU is configured to determine whether a first H-ARQ process from the set of H-ARQ processes is available for transmitting EU data in a transmit time interval (TTI). The WTRU is configured to determine whether the particular MAC-d flow has access to the first H-ARQ process, based on the information received. The WTRU is configured to transmit data from the particular MAC-d flow in the TTI using the first H-ARQ process, on a condition that the first H-ARQ process is available for transmitting EU data in the TTI and that the particular MAC-d flow has access to the first H-ARQ process.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.13/913,878 filed Jun. 10, 2013, which is a continuation of U.S. patentapplication Ser. No. 12/772,543 filed May 3, 2010, which issued as U.S.Pat. No. 8,462,717 on Jun. 11, 2013, which is a continuation of U.S.patent application Ser. No. 11/139,880 filed May 27, 2005, which issuedas U.S. Pat. No. 7,710,911 on May 4, 2010, which claims the benefit ofU.S. Provisional Application Ser. No. 60/578,712 filed Jun. 10, 2004,the contents of which are incorporated by reference as if fully setforth.

FIELD OF INVENTION

The present invention is related to a hybrid-automatic repeat request(H-ARQ) operation in a wireless communication system including at leastone wireless transmit/receive unit (WTRU), at least one Node-B and aradio network controller (RNC). More particularly, the present inventionis a method and system for dynamically allocating H-ARQ processes in theWTRU for supporting enhanced uplink (EU) transmissions.

BACKGROUND

An EU operation reduces uplink (UL) latency, improves throughput, andprovides more efficient use of physical radio resources. During EUoperation, an H-ARQ process is used to support EU transmissions betweena WTRU and a Node-B including the facilitation of a feedback process forreporting successful or unsuccessful EU data transmissions.

A number of EU H-ARQ processes are defined for each WTRU, and each WTRUsupports multiple instances of H-ARQ processes simultaneously. Since afeedback cycle for each EU data transmission is relatively long whencompared to UL transmission time, and a different number oftransmissions may be required to achieve a successful transmission foreach EU transmission, a WTRU is required to operate several H-ARQprocesses simultaneously to provide increased data rates and reducedlatency.

For any WTRU connection, multiple logical channels exist. These logicalchannels have different throughput, latency, error rates, and quality ofservice (QoS) requirements. To satisfy these requirements, the RNC setsa priority for each logical channel known as a medium access control(MAC) logical channel priority (MLP). The MLP is mapped to a dedicatedchannel MAC (MAC-d) flow which is connected to the EU MAC (MAC-e), whichmanages the EU H-ARQ processes.

A similar design exists for high speed downlink packet access (HSDPA) ina downlink (DL) channel. When higher priority data is required to betransmitted and all H-ARQ processes are already assigned fortransmission of lower priority data, it is allowed to preempt theexisting H-ARQ transmissions of lower priority with a higher prioritytransmission. When the preemption occurs, the lower priority data isrescheduled for an H-ARQ transmission at a later time.

A problem with H-ARQ process preemption is a loss of the benefit ofcombining. One important advantage of an EU H-ARQ operation is theability to store received data from previous transmissions and tocombine the previous transmissions with subsequent transmissions toincrease the probability of a successful data transmission. However,when the H-ARQ processes are preempted, the stored data of the previoustransmissions, and thus, the combining advantage of the H-ARQ processesis lost.

A reason for implementing H-ARQ process preemption is that the number ofH-ARQ processes that can be configured in the WTRU is limited. Whileeach H-ARQ process requires considerable memory for receptionprocessing, the amount of memory in the WTRU is limited.

Because it is common to have a large amount of lower priority data and asmall amount of higher priority data, when processing lower prioritytransmissions, it is necessary to avoid blocking of higher prioritytransmissions in order to maintain QoS requirements of the higherpriority data. If lower priority data monopolizes the H-ARQ processes,it may degrade overall system performance. Moreover, since lowerpriority data allows greater latency, it can result in greater H-ARQprocess holding time.

H-ARQ process preemption may solve the transmission prioritizationproblem, but at the expense of the loss of the combining benefit and,correspondingly, the less efficient use of radio resources. It isexpected that the best overall performance is achieved in H-ARQ systemswhen a large percentage of the first and possibly second transmissionsfail because a less robust modulation and coding scheme (MCS) requiringfar less physical resources can be applied. In this case, when H-ARQprocess preemption is employed, these initial transmissions andretransmissions will frequently have to be repeated to achievesuccessful transmission, which wastes radio resources utilized for theinitial preempted transmissions.

SUMMARY

The present invention is a method and apparatus for dynamicallyallocating H-ARQ processes in the WTRU for supporting EU transmissions.The H-ARQ processes in the WTRU are reserved for specific transportchannels (TrCHs), dedicated channel medium access control (MAC-d) flowsor logical channels associated with different data transmission priorityclasses. The WTRU allocates H-ARQ processes from those reserved H-ARQprocesses that are available. Optionally, a higher priority channel maybe allowed to allocate an H-ARQ process reserved for lower prioritychannels. Lower priority H-ARQ processes may be preempted. Thepreemption may be restricted by urgency of data transmission, (forexample, close to expiration of lifespan timer), or by RNC configurationof H-ARQ processes. Alternatively, a common pool of H-ARQ processes maybe configured and an H-ARQ process may be allocated from the common poolin accordance with a priority of each channel, and lower priority H-ARQmay be preempted.

In accordance with the present invention, lower priority data mayachieve maximum data rates, and higher priority transmissions may beinitiated at any time without requiring the need for H-ARQ processpreemption. By reserving H-ARQ processes for specific channels andallowing the WTRU to dynamically allocate these H-ARQ processes, the EUdata rate and transmission latency for these channels can be betterguaranteed to meet their QoS requirements.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding of the invention may be had from thefollowing description of a preferred embodiment, given by way of exampleand to be understood in conjunction with the accompanying drawingwherein:

FIG. 1 is a block diagram of a wireless communication system inaccordance with the present invention;

FIG. 2 is a flow diagram of a process for allocating H-ARQ processes ofthe system of FIG. 1 in accordance with a first embodiment of thepresent invention;

FIG. 3 is a flow diagram of a process for allocating H-ARQ processes ofthe system of FIG. 1 in accordance with a second embodiment of thepresent invention; and

FIG. 4 is a flow diagram of a process for allocating H-ARQ processes ofthe system of FIG. 1 in accordance with a third embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereafter, the terminology “WTRU” includes but is not limited to a userequipment (UE), a mobile station, a fixed or mobile subscriber unit, apager, or any other type of device capable of operating in a wirelessenvironment. When referred to hereafter, the terminology “Node-B”includes but is not limited to a base station, a site controller, anaccess point or any other type of interfacing device in a wirelessenvironment.

The features of the present invention may be incorporated into anintegrated circuit (IC) or be configured in a circuit comprising amultitude of interconnecting components.

FIG. 1 is a block diagram of a wireless communication system 100operating in accordance with the present invention. The system 100includes at least one WTRU 102, at least one Node-B 104 and an RNC 106.The RNC 106 controls overall EU operation via an Iub/Iur 112 byconfiguring EU parameters for the Node-B 104 and the WTRU 102, such asconfiguration of H-ARQ processes 124 in the WTRU 102, initial transmitpower level, maximum allowed EU transmit power or available physicalresources. An UL EU channel 108 is established between the WTRU 102 andthe Node-B 104 for facilitating EU transmissions. The UL EU channel 108includes an enhanced dedicated channel (E-DCH) for transmission of E-DCHdata and may also include a separate UL EU signaling channel. The UL EUsignaling may also be transmitted via the E-DCH.

The WTRU 102 includes a controller 122, a plurality of H-ARQ processes124, a memory 126 and a transmitter/receiver 128. The controller 122controls overall procedures of H-ARQ assignment and E-DCH transmissions.Furthermore, the controller 122 keeps track of the status of eachtransmission associated with an H-ARQ process. The memory 126 storesE-DCH data for transmission. The H-ARQ processes 124 and the memory 126may be partitioned to support a plurality of priority classes which willbe explained in further detail hereinafter.

For E-DCH transmissions, the WTRU 102 sends a channel allocation requestto the Node-B 104 via the UL EU channel 108. In response, the Node-B 104sends channel allocation information to the WTRU 102 via a DL EUsignaling channel 110. After EU physical resources are allocated for theWTRU 102, the WTRU 102 transmits E-DCH data via the UL EU channel 108.In response to the E-DCH transmissions, the Node-B sends an acknowledge(ACK) or non-acknowledge (NACK) message for H-ARQ operation via the DLEU signaling channel 110.

The memory requirement for H-ARQ operation is primarily a problem forthe receiver. For HSDPA, the number of H-ARQ processes and the memoryreserved for each H-ARQ process is minimized. For EU, the memoryrequirement in the WTRU is not as restricted as is the case for HSDPA.It is a maximum data rate that limits the minimization of the H-ARQprocesses and the memory requirements. For each “stop and wait” H-ARQprocess transmission, there is a cycle of generating the transmissionand waiting for and processing feedback for that transmission. In orderto have the ability for continuous transmission, several H-ARQ processesare required to operate in sequence.

Since the memory requirement of the WTRU 102 is not as much of a concernin EU, the number of H-ARQ processes 124 and the memory 126 reserved foreach priority class may exceed the number of H-ARQ processes required toachieve particular data rates for each priority class. The WTRU 102 canbe configured for more H-ARQ processes than that can be used at onetime. In accordance with one embodiment, the H-ARQ processes arereserved for specific TrCHs, MAC-d flows or logical channels which canbe dynamically allocated by the WTRU 102 at any time so that preemptionof an already assigned H-ARQ process and the corresponding loss of thecombining benefit can be avoided.

The H-ARQ operation may be either synchronous or asynchronous betweenthe WTRU 102 and the Node-B 104. In an asynchronous H-ARQ operation, themechanism for selecting H-ARQ processes at the WTRU 102 are not known tothe Node-B 104, therefore, the H-ARQ process should be identified ineach transmission. In a synchronous H-ARQ operation, the mechanism forselecting H-ARQ processes at the WTRU 102 are predetermined and known tothe Node-B 104. The Node-B 104 may identify the H-ARQ process used atthe WTRU 102 based on the predetermined transmission schedule. EachE-DCH transmission includes a new data indicator (NDI) indicating thatthe transmission is either a “new transmission” or a “retransmission.”The initial value of the NDI indicates that the transmission is a “newtransmission.” A retransmission sequence number of each H-ARQtransmission provides similar information. In a synchronous H-ARQoperation, the Node-B 104 can determine which H-ARQ process was used atthe WTRU 102 and what transmissions should be combined with whatprevious transmissions based on when the transmission is sent.

FIG. 2 is a flow diagram of a process 200 for allocating H-ARQ processes124 in the WTRU 102 in accordance with a first embodiment of the presentinvention. The RNC 106 configures the WTRU 102, such as the number ofH-ARQ processes 124 and/or memory partitioning associated with eachlogical channel, MAC-d flow, transport channel (TrCH) or data priorityclass are configured (step 202). This is preferably performed throughlayer-3 radio resource control (RRC) signaling procedures.

For each transmit time interval (TTI), at step 204, the WTRU 102 maydynamically allocate an H-ARQ process associated with the TrCH, MAC-dflow or logical channel being serviced. The WTRU 102 determines whetherphysical resources have been allocated by the Node-B 104 (step 206). Ifphysical resources have not been allocated, the process 200 returns tostep 204 to wait for the next TTI. If physical resources have beenallocated, the WTRU 102 selects data in the highest priority class totransmit in the current TTI (step 208). The WTRU 102 determines whatdata to transmit using a selected H-ARQ process 124, preferably based onabsolute priority. In such case, the data in the highest priority takesprecedence over data in a lower priority class each time a new H-ARQprocess is assigned.

If there is no data waiting for transmission, the process 200 returns tostep 204 to wait for the next TTI. If there is data to be transmittedand data in the highest priority class is selected in step 208, the WTRU102 determines whether an H-ARQ process 124 has already been assigned toother data having an “unsuccessful transmission” status (step 210). Ifan H-ARQ process 124 has been allocated to other data that has not beensuccessfully transmitted, (i.e., feedback information including a NACKmessage has been received), and is not waiting for data feedbackinformation, the earliest assigned H-ARQ process associated with thispriority class is selected at step 212 and the H-ARQ process istransmitted in the current TTI (step 214). The earliest assigned H-ARQprocess may be determined by either the lowest transmission sequencenumber (TSN) or the highest number of retransmissions compared to otherH-ARQ processes assigned in the same priority data.

If there is currently no H-ARQ process assigned to other data having an“unsuccessful transmission” status, the WTRU 102 determines whetherthere is an H-ARQ process associated with the TrCH, MAC-d flow orlogical channel, available for supporting the transmission of data inthis priority class (step 216). If there is an available H-ARQ process,the WTRU 102 allocates one of the reserved H-ARQ processes 124associated with the priority class of the selected data (step 218). Thepriority class may be mapped to configured H-ARQ processes associatedwith at least one of a logical channel, a MAC-d flow and a TrCH. Ifthere is no available H-ARQ process for the TrCH, MAC-d flow or logicalchannel of the selected data, the priority class is marked as beingblocked for the current TTI (step 220). The process 200 then returns tostep 208 to select the next highest priority data. The H-ARQ processesassociated with the TrCHs, MAC-d flows or logical channels supportinglower priority classes wait for a TTI where physical resources areallocated and all outstanding ready-to-transmit higher priority H-ARQprocesses have been serviced.

It is required to limit the number of H-ARQ processes required toachieve maximum data rates for each logical channel, MAC-d flow or TrCH.The RNC 106 can limit the maximum number of H-ARQ processes reserved forat least one of a logical channel, a MAC-d flow and a TrCH. Thiseffectively limits the maximum data rate of each logical channel, MAC-dflow or TrCH, when lower priority H-ARQ processes are already assigned.High priority data may have a limited number of H-ARQ processes thatlimits the maximum data rate, but still provides for low transmissionlatency. For example, signaling radio bearers (SRBs) require lowlatency, but not high data rates of traffic channels. The SRB TrCH,MAC-d flow, or logical channel may then be configured by the RNC withRRC procedures for a higher priority and one or more H-ARQ processesdedicated for this channel.

FIG. 3 is a flow diagram of a process 300 for allocating H-ARQ processesin the WTRU 102 in accordance with a second embodiment of the presentinvention. The RNC 106 configures the WTRU 102. For example, the numberof H-ARQ processes and/or memory partitioning associated with eachlogical channel, MAC-d flow, TrCH or data priority class is configured(step 302). This is preferably performed through RRC procedures.

For each TTI at step 304, the WTRU 102 dynamically allocates H-ARQprocesses. The WTRU 102 determines whether physical resources have beenallocated by the Node-B 104 (step 306). If physical resources have notbeen allocated, the process 300 returns to step 304 to wait for the nextTTI. If physical resources have been allocated, the WTRU 102 determinesthe highest priority data to transmit in the current TTI (step 308) eachtime a new H-ARQ process is assigned.

If there is no data waiting for transmission, the process 300 returns tostep 304 for the next TTI. If there is data to be transmitted, the WTRU102 determines whether an H-ARQ process has already been assigned toother highest priority data having an “unsuccessful transmission” status(step 310). If an H-ARQ process has been allocated to other highestpriority active data that has not been successfully transmitted, (i.e.,status of NACK feedback received) and is not waiting for data feedbackinformation, the earliest assigned H-ARQ process associated with thepriority class is selected at step 312 and the H-ARQ process istransmitted in the current TTI (step 314).

If there are no currently assigned H-ARQ processes for the highestpriority data, the WTRU 102 determines whether there is an H-ARQ processavailable associated with a TrCH, MAC-d flow or logical channel for thispriority class (step 316). If there is an available H-ARQ process forthe priority class of the selected data, the WTRU 102 allocates one ofthe reserved H-ARQ processes for this priority class (step 318), and theH-ARQ process is transmitted at step 314.

If there are no available H-ARQ processes for the priority class of theselected data, the WTRU 102 determines whether there are available H-ARQprocesses for lower priority class (step 320). If there are availableH-ARQ processes associated with a lower priority class, the process 300branches to step 318 to allocate the H-ARQ process associated with thelower priority class, and the allocated H-ARQ process is transmitted(step 314). If, at step 320, it is determined that there are noavailable H-ARQ processes associated with a lower priority class, thispriority class is blocked for the current TTI (step 322), and theprocess 300 returns to step 308 to select the next highest prioritydata.

Optionally, the H-ARQ processes allocated for lower priority classes maybe preempted if there is no available H-ARQ process associated with alower priority class. The RNC 106 configures the number of H-ARQprocesses reserved for each priority class. If a large number of H-ARQprocesses are reserved for higher priority data, there would be lesspreemption. If fewer H-ARQ processes are reserved for higher prioritydata, then there would be more preemption.

FIG. 4 is a flow diagram of a process 400 for allocating H-ARQ processesof the WTRU 102 in accordance with a third embodiment of the presentinvention. The RNC 106 configures a common pool of H-ARQ processes, thenumber of which exceeds the maximum number of H-ARQ processes that canbe used at any time by the WTRU 102 (step 402).

For each TTI at step 404, the WTRU 102 dynamically allocates H-ARQprocesses. The WTRU 102 determines whether physical resources have beenallocated by the Node-B 104 (step 406). If physical resources have notbeen allocated, the process 400 returns to step 404 to wait for the nextTTI. If physical resources have been allocated, the WTRU 102 selectsdata in the highest priority class to transmit in the current TTI (step408).

If there is no data waiting for transmission, the process 400 returns tostep 404 to wait for the next TTI. If there is data to be transmittedand the highest priority data is selected, the WTRU 102 determineswhether an H-ARQ process has already been assigned to other highestpriority data having an “unsuccessful transmission” status (step 410).If an H-ARQ process has been allocated to other highest priority activedata that has not been successfully transmitted, (i.e., status of NACKfeedback received), and is not waiting for data feedback information,the earliest assigned H-ARQ process associated with the priority classis selected at step 412 and the H-ARQ process is transmitted in thecurrent TTI (step 414).

If there are no currently assigned H-ARQ processes for other highestpriority data, the WTRU 102 determines whether there is an availableH-ARQ process (step 416). If there is an available H-ARQ process, theWTRU 102 allocates the available H-ARQ process (step 418), and theallocated H-ARQ process is transmitted at step 414.

If, at step 416, it is determined that there is no available H-ARQprocess, the WTRU 102 determines whether there is an H-ARQ processalready allocated for a lower priority class data (step 420). If thereis an H-ARQ process already allocated for a lower priority class data,the H-ARQ process allocated for the lowest priority class data ispreempted (step 422). The preempted H-ARQ process is allocated for theselected data and the allocated H-ARQ process is transmitted (steps 418,414). If there is no H-ARQ process already allocated for a lowerpriority class data, this priority class is blocked for the current TTI(step 424), and the process 400 returns to step 408 to select the nexthighest priority data.

Although the features and elements of the present invention aredescribed in the preferred embodiments in particular combinations, eachfeature or element can be used alone without the other features andelements of the preferred embodiments or in various combinations with orwithout other features and elements of the present invention.

What is claimed is:
 1. A wireless transmit/receive unit (WTRU)comprising: a controller, operatively coupled to a transmitter and areceiver, configured to use a plurality of hybrid automatic repeatrequest (H-ARQ) processes; the receiver configured to receiveconfiguration information that identifies at least one medium accesscontrol for dedicated channel (MAC-d) flow and identifies H-ARQprocesses, from the plurality of H-ARQ processes that the controller isconfigured to use, that data from the at least one MAC-d flow is allowedto be transmitted over; the controller configured to identify a H-ARQprocess, from the plurality of H-ARQ processes that the controller isconfigured to use, for transmission in a transmit time interval (TTI),wherein the identification is based on a predetermined schedule; thecontroller configured to select data from at least one MAC-d flow basedon the configuration information received; and the transmitterconfigured to transmit the selected data in the TTI using the identifiedH-ARQ process.
 2. The WTRU of claim 1 wherein the configurationinformation is received from a radio network controller (RNC).
 3. TheWTRU of claim 1 wherein the configuration information is received viaradio resource control (RRC) signaling.
 4. The WTRU of claim 1 whereineach MAC-d flow is associated with a priority.
 5. The WTRU of claim 1wherein the selected data includes data from a MAC-d flow associatedwith a highest priority.
 6. The WTRU of claim 1 wherein the receiver isconfigured to receive information from a radio network controller (RNC)that indicates a number of H-ARQ processes for the WTRU to use.
 7. Amethod for transmitting enhanced uplink (EU) data, implemented by awireless transmit/receive unit (WTRU), the method comprising: using aplurality of hybrid automatic repeat request (H-ARQ) processes;receiving configuration information that identifies at least one mediumaccess control for dedicated channel (MAC-d) flow and identifies H-ARQprocesses, from the plurality of H-ARQ processes, that data from the atleast one MAC-d flow is allowed to be transmitted over; identifying aH-ARQ process, from the plurality of H-ARQ processes, for transmittingEU data in a transmit time interval (TTI), wherein the identification isbased on a predetermined schedule; selecting data from at least oneMAC-d flow based on the configuration information received; andtransmitting the selected data in the TTI using the identified H-ARQprocess.
 8. The method of claim 7 wherein the configuration informationis received from a radio network controller (RNC).
 9. The method ofclaim 7 wherein the configuration information is received via radioresource control (RRC) signaling.
 10. The method of claim 7 wherein eachMAC-d flow is associated with a priority.
 11. The method of claim 7wherein the selected data includes data from a MAC-d flow associatedwith a highest priority.
 12. The method of claim 7, further comprisingreceiving information from a radio network controller (RNC) thatindicates a number of H-ARQ processes for the WTRU to use.